A properly stalled auto with considerably less HP runs as good or better time than our 6 speed counter parts? The second part is why do HP calculators seem close for 6 speeds but not stalled autos? What is about the stall that makes it appear to dyno less but yet the track tells you otherwise? Are dynos a shitty tool for autos besides a/f?

 

well the auto will have a better time becuase of the torque converter but the trap speed will be lower the auto gets off the line better the converter is basically a liquid gear ratio unlke the manual clutch which is basically a direct link......and the slip ration is why the torque converters dont let the hp on the dyno be correct

 

Elaborate more please. I and several others have large spike and even loops in Dynos, very odd!

 

not sure about that i know my buddy has a ford ranger he put a 302 in and he runs 12.98 at the track he has a 4000 stall on the dyno it says he only put down 242 which is not correct.....the dyno measures speed over time and then calculates torque.....a large converter could actually act like a slipping tranny so unless you start thr dyno run with the engine above 4000 for instance in my buddies case i dont believe it will give the correct readings.......just like if you were trying to dyno a car with a slipping tranny

 

Yeah , I've heard of dynos not catching the numbers under the stalls flash point some times.

 

i am pretty sure he is putting down around 300 with this ranger even on the 1/4 mile simulation on the dyno he only put down 262

 

Picking the right converter will make you spend most
of your gear, WOT, sitting on the horsepower peak
or close to it. You will lose some efficiency but still
see a net gain. A hard coupled powertrain has no
choice but to traverse the entire RPM band and
spend much of its time below peak HP output. This
is where dyno numbers are misleading - peak HP
tells you nothing in particular about total delivered
HP across the distance.

 

This might be able to help you understand how. I saved my dyno files last time I dyno'd so I can view them at home, and I noticed that they were in mph and thought I'd see what it'd look like with rpm on the x-axis. It actually explains a lot.

First here is my RPM graph of lid only (red) vs my car as it is now (lid, cutout, converter, all free mods, the blue graph). So I dunno if you'd want to directly compare the hp numbers, since I have different mods, even if they aren't significant power adders. Note that runs were with an unlocked converter ...


You can see that for the most part, the power is almost exactly the same (other than the top end, probably due to the cutout mostly, maybe some of the free mods). So, with the addition of the converter, the power the engine makes at a given rpm is still pretty much the same.

Now, if you look at the mph graph of the two...


You'll see a huge difference in how the HP is actually being put down at the pavement. Especially around the stall speed of the converter at ~80mph, there's a 44hp gain at the wheels! You can also see how much flatter the curve is, which means a huge under the curve gain, which you'd see even with a lower peak hp.

So while it doesn't really add power, it effectively puts you higher into the powerband much quicker, making your rpms at a certain mph higher than they were with the stock converter which in turn, gives you a lot more under the curve hp.

Another effect of a converter is the shift extension, causing the rpms to stay higher in the rpms after a shift, so instead of dropping to 3k, after a shift from 6k rpms, they only go down to 4500rpms. (somewhat bs numbers as my tach is pretty inaccurate and I've never really tried to measure it).

If you're talking about from a stop (this is where stalled auto's shine), there's also the effect of tq multiplication, or STR. My converter has an STR of 2.7. So you take 2.7 x my tq at ~3800rpm (~300 ft lbs). Which comes out to ~800 ft lbs of tq being put down from a dead stop (this effect wears off very very quickly once you're moving, plus my car still has tq managment which kills it even worse). But it gives you an idea about how my car coming off of idle can launch harder and get a better 60ft than a 6-speed launching from 6k with more hp.

So, these things added together, resulted in a .8-.9 reduction in ET from my lid only times. So, that's how you get near a second quicker with 9 more peak hp.

Sorry for the long *** post, I tried to explain everything as best I could, so I hope this makes sense, and helps answer your question. If there's anything else you need clarified, let me know and I'll try.